Presentation on theme: "Chapter 12 Genetic facts in 1900: Both female and male organisms have identical chromosomes except for one pair. Genes are located on chromosomes All."— Presentation transcript:
Genetic facts in 1900: Both female and male organisms have identical chromosomes except for one pair. Genes are located on chromosomes All organisms have two types of chromosomes: Sex chromosomes Autosomes
Male vs Female MALE Usually the Y chromosome. Y is usually smaller Male genotype = XY FEMALE Usually the X chromosome. Larger than the Y Female genotype XX Except Birds Male = XX Female = XY
Frederick Griffith British bacteriologist 1928 = designed and performed experiment on rats and bacteria that causes pneumonia. 2 strains of the bacteria Type S = causes severe pneumonia Type R = relatively harmless
Griffith’s Rats 1. First he injected living Type S bacteria into rats:
Finally he injected a mixture of living Type R and dead Type S :
Results of experiments: Because the dead rat tissue showed living Type S bacteria, something “brought the Type S back to life” Actually one bacterial type incorporated the DNA, or instructions, from the dead bacteria into its own DNA Known as transformation. Confirmed by Avery, MacLeod, and McCarty in 1944
Oswald Avery Canadian biologist (1877- 1955) Discovered DNA in 1944 with a team of scientists.
Hershey and Chase 1952 Attempted to solve the debate on whether DNA or proteins are responsible for providing the genetic material.
They used a bacteriophage (a virus which attacks bacteria) to prove that DNA was definitely the genetic material.
Exons and Introns EXONS A segment of DNA in eukaryotic organisms that codes for a specific amino acid INTRONS A segment of DNA that does NOT code for an amino acid.
Confusing genetic terms: Polypeptide = a chain of amino acids. Protein = a complex structure composed of polypeptides Amino acids = smallest structural unit of a polypeptide. Gene = a distinct unit of material found on a chromosome
Reading the genetic code The genetic code is responsible for building all the proteins in the body using 20 different amino acids. How many 3 letter words can you make from the letters A,T,G and C? Answer: 64
Codons A three letter “word” that specifies an amino acid.
tRNA (transfer) approx. 80 nucleotides in length. Cross-like shape At one end an amino acid is attached At the other end there is an anticodon Acts like a truck
Polypeptide assembly Translation = reading or “translating” the RNA code to form a chain of amino acids. Known as protein synthesis Occurs in the cytoplasm. (p.304)
Mutations The source of variation in a genetic sequence. Can be either gene or chromosomal mutations. Point mutations = a change in a single nucleotide in a sequence of DNA.
Frameshift Mutation Inserting an extra nucleotide which, in turn, shifts the entire sequence one way or the other.
Chromosomal mutations Involves a change in the number or structure of the chromosomes. Deletion : when a piece of a chromosome breaks off and is lost. Duplication : when a segment of a chromosome is repeated Inversion : when a segment of a chromosome is reversed.
More chromosomal mutations Translocation : when part of a chromosome breaks off and is attached to a non- homologous chromosome.
Control of gene expression Genes are often like light switches that can be turned off and on. Operon = occur in prokaryotes. (bacteria) different genes that work together to activate gene functions
Eukaryotic gene expression Controlled by complex sequences of DNA. Example: “TATA box”
Factors: Overall gene control is more difficult for eukaryotes because functional genes may be on different chromosomes. Environmental such as chemicals and temperature.
Hox and Oncogenes Hox genes Genes that actively control embryonic development. Oncogenes Genes known to cause cancer. Usually these are switched “off”, but can be switched “on” by a number of factors.
Assignment: Pages 315-116 1-10, 13, 15, 19, 20, 23 Transcribe this DNA sequence into RNA, then translate the RNA into an amino acid chain: TAGCCGACAGGCCTCTTTACT 1-12 page 317